[On the origin of the adaptative immune system (AIS): the hypothesis]

The adaptive immune system (AIS) appears exclusively at the vertebrate ones with jaw. In parallel, the lymphoid tissu associated with the digestive tract, or GALT (gut associated lymphoïd tissu), seems to play an essential part in the development of this response immune with memory. That one could find its origin in the innate immune system of the invertebrates and closer the cyclostomes (vertebrates without jaws). But the transition is brutal since the chondrychtyens (lines, sharks) do have the AIS but the cyclostomes not. Moreover, it is still enigmatic and source of speculations. The gnathostomes (vertebrate with jaw) raise ancestral and adaptive innate defences of which acquisition will be discussed here. We will also discuss the consequences of integration in the genome by rag1 and rag2 genes (recombination activating genes).